The live action version of Moose was portrayed by Cody Kearsley in Riverdale.
Moose is blessed with great strength. In one sequence, he slides under a car and, from his supine position, lifts it off the ground. As a result, people often have high expectations of him regarding athletics. He has helped Riverdale High School win many matches in basketball, baseball, football, ice hockey, and various other sports, though he seems to have a preference for football. Moose was originally created to serve as the personification and stereotype of the jock—all brawn and no brains. In the Spanish version of the comic, Moose is called Gorilón ("Big Gorilla"). In at least one story in the 1950s, Moose gives his real name as Merton Matowski.
His various tendencies may be inherited from one of his first ancestors to immigrate to the United States. In one story, a Russian named Lazslo Kharandashikov befriends Archie Andrews's Scottish ancestor Andy Andrews when they meet on the same ship immigrating to the US. Laslo protects Andy from another man who wants to thrash Andy. Andy shows gratitude by finding Laslo's immigration money for him after Laslo nearly loses it. Laslo's difficulty in speaking English leads him to give his name as "Mason" to the immigration officials who let him into the country.
In some stories one of the gang, usually Archie, asks for Moose's help with a problem that can only be solved by means of the big guy's strength or intimidating presence. In "Guardian Devil," Archie and Betty meet a runaway child whose hospitalized mother left the boy in her brother's care, but the uncle locked the boy in his room and had wild parties in the house—until Archie brought Moose over to straighten things out; after manhandling the uncle, the intimidating Moose sends the partygoers running with the simple exclamation "Scat!". In another story, Archie had tracked down two thugs who robbed the Chok'lit Shoppe, using a description given by Jughead, whom the cops had found in the store and initially accused. The thugs had just started beating Archie when Moose showed up; he picked the thugs up effortlessly and took them to the police station.
While Moose is easily angered and will threaten to hurt those who upset him, he is very kind, loyal, and compassionate. He is always willing to help somebody in need, and he constantly protects his friends from bullies (often without using punches). He also cares for the well being of animals and small children. In one story, two young children vandalize a classroom in Riverdale High School but Moose takes the blame for them.
Moose is the son of Jerry and Marilyn Mason.
Like most characters, Moose has a sibling who is only featured a few times. Marsha Mason, Moose's freshman sister, is featured in Betty and Veronica Double Digest #20 in "Moose's Sister" (Parts 1 & 2). Marsha starts school at Riverdale High School, and Reggie Mantle began dating her. After two weeks of dating, Moose finds out and beats up Reggie for dating his sister. Marsha has been seen before as a cameo in comics.
Moose is extremely possessive of Midge Klump, his steady girlfriend, and has time and again flattened anybody (Reggie Mantle is his most frequent victim) who seeks her affection. This possessiveness is at times taken to extremes. He's wary of any male even speaking to her, and has at times assaulted even his best friends, inflicting injuries that should, by all rights, be life-altering. There are times when Midge cannot stand Moose's jealousy and ends up scolding him, but every time he just wants to give Midge some space, she decides that she prefers the old Moose.
He has threatened Archie before for various things, but since he knows that Archie is not anywhere near interested in Midge as a girlfriend, this allows Moose to be more tolerant of Archie. At one time, a computer matched Archie and Midge, to Moose's fury, but Archie and Midge both stated that they weren't interested in each other, except as friends, which allowed Moose to cool off. At one point, Archie outright asks permission to date Midge, and Moose declined the request, but it showed, that at least Archie has the courtesy to ask him, whereas Reggie will stoop to dating her on the sly-which often results in Moose pounding up Reggie-as a running gag.
Archie was once able to use Moose's devotion and genuine concern for Midge to help him defeat a gang of robbers who were stealing office electronics from the school. The robbers managed to bind and gag Archie and Jughead and appeared to be getting away, until Archie spotted Moose playing handball on the school grounds through a window. Archie managed to slip a note out the window to Moose saying Midge was the one being held. An angry Moose quickly subdued the gang and freed Archie and Jughead. Rather than being angry over the deception, Moose showed relief that Midge was not in any danger and joked that stopping the crooks was more exciting than playing handball was.
Moose has a mean streak in many comics, and spends a lot of time hiding behind park benches inhabited by his girlfriend, Midge. He does this so that whenever somebody comes along to talk to her, he can jump out and beat him up. Often, these are false alarms; someone just happens to be in the wrong place at the wrong time. In Archie comics as late as the 1970s, Moose sported a flattop haircut. Also, in earlier days, whenever Moose talked he would start off with a "D-uh", decades before it became a synonym for something so obvious that everyone should know it. When Moose says it, he is not being sarcastic. He seems to have tried both a modified moptop and a modified flattop in recent years.
He it is often said that he consistently scores straight F's (which, at one point, he thought meant Fantastic). Moose's learning difficulties were later revealed to be dyslexia, which made it harder for him to understand what his teachers, such as Miss Grundy, were writing on the chalkboard. However, Moose's friends never want to see him fail and are always willing to help him study. Moose has done better at school when he needs to, and is able to understand complex subjects like algebra if people explain them to him enough—something which nearly drove Reggie Mantle crazy when he acted as Moose's math tutor.
A theme used in many stories is based on the Riverdale High rules that failing students are not allowed to participate in extracurricular activities. At such times, Moose has to pass a makeup test, and proves to have difficulty studying. Coach Kleats and Moose's teammates depend on Moose to help them win most of their games. Moose can always depend on a friend to tutor him, and he almost always passes the test makeup test. However, sometimes their efforts backfire, and they do not win the game even if he did pass.
In today's Archie world, Moose isn't as dumb as he appears. He was offered a full football scholarship to a University. When he found out that they wanted to place him into "joke classes" so he would get good grades, he turned down the offer. When asked about it, he replied "I may be dumb, but there's no reason for me to stay dumb." He also briefly dropped out of high school, but returned upon realizing he would need a college education to get the jobs he would like to try.
Despite his limited intelligence, Moose has a deeply sensitive side, which many people do not see. The first person he opens up to is Dilton Doiley. Moose has a deep admiration of Dilton because of his intelligence; Moose calls him his "little buddy" and will go to any length to help the diminutive genius. When Moose feels discouraged by other people's opinions of him, Dilton is the first to stick up for him. In one story, walking through the snow, the two discuss Moose's thoughts and feelings. At this point, Dilton finds that despite what people think of him, Moose has a poetic and philosophical view of certain things.
Moose has appeared briefly in one episode of the Simpsons, along with Archie, Reggie and Jughead, where they drive up to the Simpsons' house and dump Homer unceremoniously onto the front lawn. Moose then warns Homer to "Stay outta Riverdale!" Later, Homer, while reading an Archie comic, calls them all "stuck-up Riverdale punks."